Difference Between Limestone and Marble

Both limestone and marble are types of rock made of calcium carbonate residues. Even though their chemical nature is almost similar to each other, there are many differences between limestone and marble in the way they originate and the physical characteristics they possess. In general these are used as construction material and as raw material for various other industries.

Limestone

Limestone mainly consists of two types of minerals; namely, calcite and aragonite. These are two different forms of calcium carbonate itself. The source of these calcium depositions are usually the left-over shell secretions/skeletal fragments of marine organisms such as corals. Therefore, limestone is a type of sedimentary rock formed by the deposition of material at the earth’s surface or within water bodies. Sedimentation can take place at the site of the source or at a completely different location. If it’s at a different location, these sediments are transported to the location of deposition by water, wind, ice etc.

Limestone is soluble in weak acidic media generally and sometimes even in water. Depending on the pH value of water, temperature of water, and ion concentration, calcite may remain as a precipitate or dissolve. Therefore, limestone can only barely survive in water and, when in deep water bodies, it dissolves due to high water pressure. Most ancient caves were naturally formed due to the erosion of large bodies of limestone by water over thousands of million years. Clay, silt and sand from rivers together with bits of silica (from the remains of marine organisms) and iron oxides are the most commonly found impurities in limestone. Due to the presence of these impurities in varying amounts, they exhibit different colours. Depending on the method of formation it can take different physical shapes. i.e. crystalline, granular, large rock type.

Limestone was most famous during the 19th and 20th century as many public buildings and structures were made from limestone. The Great Pyramid of Giza which is one of the Seven Wonders of the World is also made of limestone. Kingston, Ontario, Canada is nick-named the ‘Limestone City’ as many buildings are constructed from limestone. As raw material in the manufacture of cement and mortar, crushed as a solid base for roads, added as white pigment in medicines, cosmetics, toothpastes, paper, plastics etc. are among the many other uses of limestone.

Marble

Marble is formed when the carbonate material in limestone gets recrystallized. This happens through a process called ‘metamorphism’ which means the “change in type”. Metamorphic rocks are born when existing rock types are transformed physically/chemically due to high temperatures and pressure; hence limestone gives birth to marble when transformed. The name ‘marble’ is derived from a Greek word meaning “shining stone”. Pure white marbles are obtained from very pure forms of limestone or dolomite rock, and the colored marbles are a result of impurities present in the parent rock. Generally high amounts of magnesiumin limestone give a greenish tint to the marble.

Marble is most commonly used for sculpture and as construction material. Since ancient days, marble sculpture has had its cultural affiliations, especially among the Greek and Roman architects who commonly used it as a decorative stone. Nowadays, synthetic marble is also been produced by mixing marble dust with cement and other resins. Among the top marble producing countries are Italy, China, India and Spain.

What is the difference between Limestone and Marble?

• Limestone is a type of sedimentary rock formed by the deposition of natural carbonate material, whereas marble is a type of metamorphic rock formed by metamorphism of limestone.

• The internal carbonate crystal structure of limestone and marble are different to each other.

• Marble is more expensive than limestone and is famous for its sculptures.